In order to view treponema pallidum, the causative agent of syphilis, under the microscope, you can tag the specimen with an antibody-fluorescein dye complex and look under a microscope that projects uv light onto the specimen. what test are you using?

a. western blot test
b. fluorescence antibody (fa) test
c. kirby-bauer disc diffusion test
d. elisa test
e. agglutination test

The correct answer is b. Fluorescence antibody (FA) test

Explanation:

The fluorescence antibody test is used to detect particular antigen which can be present in the patient's body.  Antibodies attached with a fluorogen is used to detect the antigen by emitting light under a florescent microscope which signifies the infection of that bacteria in patient.

In the case of syphilis, a smear of T. pallidum is made on a glass slide then patient serum is spread over it. Then serum is washed off and a secondary antihuman antibody with attached fluorogen is added to the smear.

On examination under microscope T. pallidum will only be seen if antibodies from patient serum are bounded with bacteria because secondary antibody will bind to human antibody only. Fluorescence confirms the presence of T. pallidum infection in patient.